The dynamic buckling behaviours of functionally graded (FG) rods reinforced with graphene platelets (GPLs) under axial impact are comprehensively analysed using the energy method, with particular emphasis on explicitly accounting for the effects of stress wave propagation. The effective material properties are determined using modified Halpin-Tsai and Voigt-Reuss models for three distributions of GPLs through the thickness. Accounting for stress wave effects, a Lagrange function is formulated with trial functions satisfying boundary conditions. A time-dependent governing equation is derived and solved for three constraint types to obtain the critical buckling velocities. Numerical results examine how distribution patterns, geometry, GPL content, impact mass, and boundary conditions affect the critical velocities. The main findings highlight that impact-induced buckling is not instantaneous but rather a time-dependent process that varies significantly across different GPL distributions, providing crucial insights for the impact-resistant design of FG composite structures.
This study investigates the fatigue behavior of glass fiber reinforced vinyl ester and unsaturated polyester composites modified with core–shell rubber particles (CSRP) under fully reversed tension–compression fatigue loading ( R = −1). A stiffness-based framework is adopted to characterize damage evolution and structural durability. Laminates containing 0, 2, 5, and 10 wt% CSRP were evaluated, with 5 wt% identified as the optimal modification level, preserving stiffness and strength while enhancing deformation capacity. Under cyclic loading at 40%–80% of the control compressive strength, CSRP-modified systems demonstrated fatigue life improvements of up to approximately 5.4×, particularly in the intermediate stress regime. A three-stage stiffness degradation model was developed to quantify damage progression, capturing early saturation, progressive degradation, and final failure. The modified systems exhibited reduced mid-life degradation rates (up to 52% in vinyl ester and 19%–23% in unsaturated polyester). Serviceability-based durability maps further showed improvement factors of 3–7 within the 50%–70% stress range. Fatigue stabilization is attributed to matrix-level toughening, where CSRP inclusions promote stress redistribution and delay crack coalescence. These results establish a direct link between matrix modification and improved fatigue durability in composite materials.
The demanding operational environments of advanced aerospace vehicles urgently require electromagnetic wave (EMW) absorbing materials that simultaneously possess broad bandwidth and exceptional high-temperature stability. ZrB 2 exhibits great potential as an EMW absorber due to its excellent electrical conductivity; however, its application is severely limited by surface-induced impedance mismatch. Herein, we demonstrate that the electromagnetic attenuation behavior of nano ZrB 2 is governed by its surface states, which dictate the trade-off between impedance matching and conduction loss. To exploit this mechanism, surface-tuned ZrB 2 nanoparticles were integrated into a polymer-derived SiOC ceramic matrix. Benefiting from the synergy between enhanced micro-conduction networks and optimized impedance matching enabled by surface engineering, the resulting composites exhibit superior cross-band EMW absorption. Specifically, the composite achieves a remarkable effective absorption bandwidth (EAB) of 10.8 GHz (7.2–18.0 GHz), successfully covering the entire X and Ku bands as well as a segment of the C band, at a matching thickness of 4.1 mm. These findings elucidate the role of nanostructure surface states in regulating dielectric behaviors, providing insights for designing next-generation, high-temperature EMW absorbers for advanced stealth applications.
Elastomeric composite material exhibit a highly nonlinear mechanical response that varies significantly with the applied deformation mode, particularly under large strain conditions. This behavior makes the selection of an appropriate hyperelastic constitutive model essential for achieving reliable numerical predictions. In this study, the uniaxial tensile and compressive behaviors of elastomeric composite material are experimentally investigated and subsequently reproduced through finite element simulations conducted in Abaqus software. Several commonly used hyper elastic strain-energy formulations, including Ogden models of different orders and Reduced Polynomial models, are identified using experimental stress–strain data and systematically compared. The results show that although lower-order models can represent the initial stiffness with reasonable accuracy, they fail to adequately describe the response at large deformations. Among the examined formulations, the sixth-order Ogden model provides the closest agreement with experimental results in tension, accurately capturing the pronounced strain-stiffening behavior observed at high stretch levels. In contrast, the second-order Reduced Polynomial model offers superior performance in compression by effectively reproducing both the initial softening response and the subsequent stiffness increase associated with material densification. These findings confirm the strong dependence of hyper elastic model performance on deformation mode and demonstrate that different constitutive formulations may be required for tensile and compressive loading conditions. The results provide practical guidance for the numerical modeling and design of sandwich structures incorporating elastomeric composite material cores.
Thermoplastic composites are widely adopted for their recyclability, rapid processing, high toughness, and impact resistance. However, comprehensive temperature-dependent datasets for accurate process modeling, along with an understanding of how polymer transition temperatures and associated molecular mobility govern the evolution of macroscopic properties, remain limited. This study presents the temperature-dependent thermal, physical, and mechanical behavior of unidirectional carbon fiber-reinforced polyamide 6 (CF/PA6) composite tape. Through experimental characterization, the relationships between polymer transition temperatures, matrix molecular mobility, and the resulting variations in material properties are established. The results reveal that the specific heat capacity, thermal expansion, density, and thermal transport properties evolve with temperature in response to changes in molecular mobility near the glass transition and melting temperatures of the polymer matrix. Mechanical testing demonstrates a gradual reduction in longitudinal properties, with fiber reinforcement continuing to provide structural support, in contrast to the pronounced temperature sensitivity and drastic decline observed in transverse and shear properties as the matrix softens. Therefore, this study provides a critical dataset for modeling and simulation efforts and offer essential insights into how polymer transition temperatures and associated molecular mobility govern the evolution of macroscopic properties.
